After a prologue and 13 stages, the Tour de France enters its piece de resistance. This year, it's four stages of pure climbing hell in five days in the Pyrenees. At the end of this savage test, there will be no doubt who deserves to wear the maillot jaune.

Barring an accident or illness, the race will be won by either Alberto Contador or Andy Schleck. They have clearly separated from the pack and they will be duking it out in the next four stages. There will be more desperation on Schleck's part, even though he has a 31-second lead. He knows he must have at least a 2-minute, maybe a 3-minute, lead after the Pyrenees to have a chance to keep the yellow jersey.

Can Schleck do it? We would say no. They're both very aggressive riders and both will seek to attack first to put the other on the defensive. Schleck might put Contador temporarily in trouble, but it'll require a herculean effort to gain two minutes on the indefatigable Spaniard.

Let's take a look at those four stages and see who has the edge:

Stage 14 (Revel to Ax 3 Domaines)

This stage will unfurl in a pretty benign fashion before reaching a crescendo with the final two climbs. The first, up the HC Port de Pailheres is longer and maybe a bit harder, but the selection will come at the final climb, 7.8 km up Ax 3 Domaines on an 8.2% gradient.

Advantage: Schleck. The climbs are not terribly savage until the end and Schleck's team is fresh. It sets up well for Saxo Bank to dictate the pace and for Schleck to launch the first attack. Prediction: Schleck wins this stage with Contador close behind.

Stage 15 (Pamiers to Bagneres-de-Luchon)

This may be the easiest of the four stages, with three moderate climbs before the final climb up HC Port de Bales. And it concludes on a 20-km very technical descent to the finish. The route passes a white marble memorial of Fabio Casartelli, who died on a descent of Col de Portet d"Aspet during the 1995 Tour. His Motorola teammate won Stage 18 three days later and paid tribute to his fallen comrade. It was Lance Armstrong's last Tour stage win before he was stricken with cancer.

Advantage: Neutral. Any time gained on the attacks here may be offset on the descent so it doesn't set up well for an attack. Look for a breakaway climber to succeed here as the main GC contenders will try to use this stage to conserve some energy. Prediction: A breakaway succeeds as Schleck and Contador fight to another draw.

Stage 16 (Bagneres-de-Luchon to Pau)

This will be the hardest stage in this year's Tour, with four climbs rated either HC or Cat. 1, including the first pass through Col du Tourmalet. The final climb is not terribly steep, but it's long, at nearly 30 km, up Col d'Aubisque. After that, it's a 60-km downhill ride to the finish in Pau.

Advantage: Neutral. It's more of a war of attrition. With such a long, descending finish, this stage will not act as a big selection for the main contenders. A breakaway pack also may succeed here as the GC contenders will not try to reel back anybody who's not remotely close to a podium finish.

Stage 17 (Pau to Col du Tourmalet)

The Tour celebrates its 100 years in the Pyrenees with an appropriately brutal stage. It begins with two Cat. 1 climbs before the second pass through Col du Tourmalet, but this time from the more difficult western side, where no Tour stage has ever been contested before. The final climb is nearly 20 km long with an average gradient of 7.5%.

Advantage: Contador. If he's either leading or trailing close behind Schleck at this point, look for a tactical ride by Contador early on before launching a final attack that would serve as the coup de grace. Though Contador knows he's better than Schleck in the time trial, he'd rather not take any chances there and allow Schleck to go into the penultimate stage with the maillot jaune.